In recent years, due to tightened regulations on gas emission from an internal combustion engine of an automobile or the like, a fuel spray injected from a fuel injection valve is required to be atomized.
In particular, various examinations have been conducted on the atomization of the fuel spray.
For example, there is known a fuel injection valve including an injection-hole plate formed by laminating an upstream-side plate and a downstream-side plate. An inner diameter-side inner wall surface of an upstream-side injection hole formed through the upstream-side plate is formed continuous with an inner diameter-side inner wall surface of a downstream-side injection hole formed through the downstream-side plate. A guide portion for guiding a fuel flow toward the inner diameter-side inner wall surface of the downstream-side injection hole is formed at least on an inner wall surface of the upstream-side injection hole on an outer diameter side (see Patent Literature 1).
In the fuel injection valve described above, the fuel reaching the vicinity of the outer diameter-side inner wall surface of an inlet-side opening edge of the upstream-side injection hole is subjected to a guiding action of the guide portion to be guided to the inner diameter-side inner wall surface of the downstream-side injection hole. In this manner, the fuel is formed into a liquid film along the inner wall surface of the downstream-side injection hole, and is then atomized by the injection.
Further, there is also known a fuel injection valve in which second cylindrical holes are formed through a downstream-side injection-hole plate to be held in communication with a plurality of first cylindrical holes formed through an upstream-side injection-hole plate in a one-to-one relationship, and each of the second cylindrical holes has a larger hole diameter than that of the first cylindrical holes and is inclined at a predetermined angle with respect to the first cylindrical hole (see Patent Literature 2).
In the fuel injection valve, a fuel liquid passing through the first cylindrical holes reliably collides against inner wall surfaces of the inclined second cylindrical holes to be injected in a thin liquid-film form along the inner wall surfaces while spreading on the inner wall surfaces of the second cylindrical holes to both sides in a circumferential direction, and thus the fuel liquid is atomized.